This invention relates to a fuel metering device for low fuel feed pressures and adapted for use in externally ignited internal combustion engines of the air/fuel mixture-compressing type with conduit means for conveying fuel to the suction pipe of the engine, in which conduit means at least one throttle passage of determinable cross-sectional area is arranged.
In an internal combustion engine, such a fuel metering device serves for attaining, automatically and under all operational conditions, a favorable fuel/air mixture ratio, in order to burn the fuel as completely as possible and thereby to avoid or substantially reduce the production of toxic exhaust gases while maintaining an optimal performance of the internal combustion engine with the smallest possible consumption of fuel. To this end, it is necessary that, when starting a cold engine, the fuel/air mixture is "richer" during the warming-up phase, i.e., the fuel portion in the mixture must be larger, than when the engine is warm. However, even in a hot engine it is necessary to meter the fuel in amounts corresponding very accurately to the requirements of every operating condition of the internal combustion engine. Therefore, the proportionality of the amounts of air and fuel in the mixture must be variable, in dependence on such engine data as speed, load, and temperature, as well as on environmental data such as air humidity, atmospheric pressure, and ambient temperature.
In the case of a known fuel metering device of the initially described type, complicated control systems must be provided to meet the above-stated requirements.